## Leaf spring design

## Leaf spring design

(OP)

Hi,

Can anyone help with pointing me in the right direction for design calculation of leaf spring capable of taking loads of 1000kg to 3000kg - For use on slow moving vehicules

Jan

Can anyone help with pointing me in the right direction for design calculation of leaf spring capable of taking loads of 1000kg to 3000kg - For use on slow moving vehicules

Jan

## RE: Leaf spring design

## RE: Leaf spring design

However, to get you going, here is the formula for a multileaf spring, from the Bosch Blue Book

Bending stress= 3*length*Force/(width*N*thickness^2)

N is the number of leaves in the middle, n is the number at the end

rate=(2+n/N)*E*N*width*thickness^3/(6*length^3)

This leaf spring is triangular in side view, ie each leaf is a fixed amount shorter than the one above.

The Devil is definitely in the details, which is where the SAE book will help.

Cheers

Greg Locock

## RE: Leaf spring design

I have had a go at the formula you have shown. Just a few questions ….

If length, width and thickness is in m, Force in Newton’s. N is the number of leaves at the end. i.e. next to the eye … With 8 springs and 2 at the end (1 is the top spring with the eye) The other 6 are then evenly shorter …right ??

The calculated rate is then the movement in m (from the centre of the spring) for each N applied to the spring ??

E = Youngs Modulus for the material used.

Or have I got myself barking up the wrong tree here ….

Appreciate you comments on this …

Jan

## RE: Leaf spring design

Cheers

Greg Locock

## RE: Leaf spring design

Thanks for your reply. I think I must have a decimal error. With ….

L = 0.89m

F = 24516N

W = 0.05m

N = 8

n = 2

t = 0.04m

E = 210000 MN/m^2

The rate is 2.86m … clearly not right ….?? I must have missed something ….

Regards

Jan

## RE: Leaf spring design

Norm

## RE: Leaf spring design

Norm

## RE: Leaf spring design

I don't see how you got 2.86, I think you've got an arithmetic error.

I'd use a t of more like .015, and more leaves, for this design.

You probably want 400-2000 N/mm (roughly) as a rate

Cheers

Greg Locock

## RE: Leaf spring design

Regards

Jan

## RE: Leaf spring design

Can you please explain why I can only get a sensible answer when I use 210x10^6 for E. I thought E should have been 210x10^11 (in Newtons)

Regards

Jan

## RE: Leaf spring design

E for steel should be 210*10^9 N/m^2 or 210*10^9 N/m^2.

regards desertfox